Denitrification in the rhizosphere of rice and wheat seedlings as influenced by Plant K Status, air-filled porosity and substrate organic matter

Abstract

The effect of K. deficiency on denitrification in the rhizosphere was studied with wheat and rice plants which are different in aerenchyma formation. The seedlings were grown in carbon-free quartz silt, except for one experiment where cellulose was added. With K sufficient as well as with K deficient plants denitrification increased exponentially, when air-filled porosity of the substrate declined below a threshold of 10–12%. With wheat the increase in denitrification was higher with K deficient individuals. Epidermal and cortical cells of K deficient wheat roots collapsed and became invaded by microorganisms. For rice roots rhizosphere denitrification was generally lower than for wheat roots. K deficient rice roots had not collapsed and did not support higher denitrification in the range of the air-filled porosities tested. Addition of cellulose as a slow-release carbon source enhanced denitrification for K sufficient but not for K deficient rice plants.